[P4d] Create TUI sidebar component for token-meter

[four-bytes-robby]

Purpose

TUI sidebar component showing live token usage with color-coded progress bar. Subscribes to plugin bus for real-time updates.

Scope

TUI component (src/tui.tsx)

• @jsxImportSource @opentui/solid
• Sidebar slot: sidebar_content
• Auto-refresh: subscribes to tbg/+/status via BusTui
• Progress bar: width = percentage, color:
  • Green (< 50%): tokens well within budget
  • Yellow (50-80%): approaching soft limit
  • Red (> 80%): near hard limit
• Display: token count, percentage, status text
• Truncated session ID

BusTui integration

• Import BusTui from @four-bytes/opencode-plugin-lib/tui
• On mount: connect to bus, subscribe to tbg/+/status
• On message: update SolidJS signals
• On unmount: unsubscribe, close connection
• Auto-reconnect handled by BusTui

Startup message

• If no bus running: show "plugin bus not available" for 3 seconds, then hide
• If bus running but no TBG session: show "waiting for session..."

Files

• src/tui.tsx (new)

Depends on

• [P17] Go Plugin Bus v0.1.0
• [P17b] @four-bytes/opencode-plugin-lib v0.2.0 (./tui export)
• [P4d] TBG publishing to bus (issue feat: initial skeleton — package, hook, token-estimation, diary #2 above)

Acceptance

• TUI sidebar renders with progress bar
• Updates in real-time as tokens accumulate
• Color changes at threshold crossings
• Shows "plugin bus not available" when bus is down